The present invention is concerned with ionic compounds derived from malononitrile in which the anionic charge is delocalized, and their uses.
It is known and particularly interesting to introduce ionic groups in organic molecules or polymers having various functions. Coulombic forces correspond, indeed, to the stronger interactions which are available at the molecular level, and the ionic groups modify in a very noted manner the molecules to which they are attached. Coloring materials which are made soluble in water by means of sulfonate or carboxylate functions may be mentioned.
However, the xe2x80x94CO2xe2x88x921/mMm+ or xe2x80x94SO3xe2x88x921/mMm+ groups of this type are not dissociated, and they cause no solubility in solvents except water or certain highly polar protic solvents such as light alcohols, which considerably restrict the scope of their use.
On the other hand, salts of the compounds [RFSO2xe2x80x94Nxe2x80x94SO2RF]xe2x88x921/mMm+ in which RF is a perfluorinated group and Mm+ is a cation of valence m+ which are soluble and are dissociated in ordinary aprotic media or solvating polymers, are known. It is however considered that the existence of two perfluoroalkylsulfonyl groups (in particular the existence of fluorine atoms on the a atom of carbon of each sulfonyl group) which exert an important attracting power on the electrons of the anionic charge, is a necessary condition to obtain properties of solubility and dissociation. For example, the pKa of the acid H[CF3SO2xe2x80x94Nxe2x80x94SO2CF3] is only 1.95, as compared to that of the non-fluorinated acid CH3SO3H (pKa=0.3) and is clearly inferior to that of the perfluorinated acid CF3SO3H (pKa less than xe2x88x929) because of the basic character of the central nitrogen atom.
Surprisingly, the inventors have found that the compounds containing ionic groups xe2x80x94C(CN)2xe2x88x92 have excellent properties of solubility and dissociation, even when they contain no highly electroattractive perfluorinated groups.
The present invention consequently aims at supplying a family of ionic compounds having a good solubility and a good dissociation, without requiring complex modifications of the starting molecule. The precursors of the molecules of the invention are for the most part industrial products and/or easily accessible. In addition, it should be noted that the absence, or at least the decrease of the perfluorinated fraction in the compounds of the invention, enables to reduce production costs of the compounds and consequently the cost of the resulting applications.
An object of the present invention is an ionic compound which is a derivative of malononitrile comprising an anionic part which is associated to at least one cationic part M+m in a sufficient number to provide for the electronic neutrality of the whole, characterized in that M is a hydroxonium, a nitrosonium NO+, an ammonium xe2x80x94NH4+, a metallic cation having a valency m, an organic cation having a valency m or an organometallic cation having a valency m, and in that the ionic part corresponds to one of the formulae RDxe2x80x94Yxe2x80x94C(Cxe2x89xa1N)2xe2x88x92 or Zxe2x80x94C(Cxe2x89xa1N)2xe2x88x92 in which:
Z represents an electroattractor radical having a Hammett parameter at least equal to that of a phenyl radical, selected from:
j) xe2x80x94CN, xe2x80x94NO2, xe2x80x94SCN, xe2x80x94N3, FSO2xe2x80x94, xe2x80x94CF3, Rxe2x80x2FCH2xe2x80x94 (Rxe2x80x2F being a perfluorinated radical, preferably CF3xe2x80x94), fluoroalkyloxy, fluoroalkylthioxy, fluoroalkenyloxy, fluoroalkenylthioxy radicals;
jj) radicals comprising one or more aromatic nuclei possibly containing at least one nitrogen, oxygen, sulfur or phosphorus atom, said nuclei possibly being condensed nuclei and/or said nuclei possibly carrying at least one substituent selected from halogens, xe2x80x94CN, xe2x80x94NO2, xe2x80x94SCN, xe2x80x94N3, CF2xe2x95x90CFxe2x80x94Oxe2x80x94, radicals RFxe2x80x94 and RFCH2xe2x80x94 in which RF is a perfluoroalkyl alkyl having 1 to 12 carbon atoms, fluoroalkyloxy groups, fluoroalkylthioxy groups, alkyl, alkenyl, oxa-alkyl, oxa-alkenyl, aza-alkyl, aza-alkenyl, thia-alkyl, thia-alkenyl radicals, polymer radicals, radicals having at least one cationic ionophorous group and/or at least one anionic ionophorous group;
xe2x80x83with the proviso that one substituent Z may be a monovalent radical, a multivalent radical, or part of a multivalent radical (including a dendrimer) carrying at least one group xe2x80x94C(Cxe2x89xa1N)2, or a segment of a polymer;
Y represents a carbonyl group, a thiocarbonyl group, a sulfonyl group, a sulfinyl group or a phosphonyl group and:
RD is a radical selected from:
a) alkyl or alkenyl radicals, aryl, arylalkyl, alkylaryl or alkenylaryl radicals, alicyclic or heterocyclic radicals, including polycyclic radicals;
b) alkyl or alkenyl radicals comprising at least one functional ether, thioether, amine, imine, amide, carboxyl, carbonyl, isocyanate, isothiocyanate, hydroxy;
c) aryl, arylalkyl, arylalkenyl, alkylaryl or alkenylaryl radicals, in which the aromatic nuclei and/or at least one substituent of the nucleus comprises heteroatoms such as nitrogen, oxygen, sulfur;
d) radicals comprising condensed aromatic cycles which possibly comprise at least one heteroatom selected from nitrogen, oxygen, sulfur;
e) halogenated or perhalogenated alkyl, alkenyl, aryl, arylalkyl, alkylaryl radicals, said radicals possibly comprising functional ether, thioether, imine, amine, carboxyl, carbonyl or hydroxy groups;
f) radicals RCC(Rxe2x80x2)(Rxe2x80x3)xe2x80x94Oxe2x80x94 in which RC is an alkyl perfluorinated radical and Rxe2x80x2 et Rxe2x80x3 are independently from one another a hydrogen atom or a radical such as defined in a), b), c) or d) above [for example CF3CH2Oxe2x80x94, (CF3)3COxe2x80x94, (CF3)2CHOxe2x80x94, CF3CH(C6H5)Oxe2x80x94, xe2x80x94CH2(CF2)2CH2xe2x80x94];
g) radicals (RB)2Nxe2x80x94, in which the radicals RB which are identical or different are such as defined in a), b), c), d) and e) above, one of the RB may be a halogen atom, or the two radicals RB together form a divalent radical which constitutes a cycle with N;
h) polymer radicals;
i) radicals having one or more cationic ionophorous groups and/or one or more anionic ionophorous groups;
xe2x80x83with the proviso that one substituent RD may be a monovalent radical, part of a multivalent radical carrying a plurality of xe2x80x94Yxe2x80x94Cxe2x88x92(Cxe2x89xa1N)2 groups or a segment of a polymer;
xe2x80x83with the proviso that when Y is a carbonyl and RD is a perfluoroalkyl radical having 1 to 3 carbon atoms, or when Z is xe2x80x94CN, M is different from an alkali metal.
According to an embodiment of the invention, the cation is a metallic cation selected from cations of alkali metals, cations of alkali-earth metals, cations of transition metals, cations of trivalent metals, cations of rare earths. By way of example, Na+, Li+, K+, Sm3+, La3+, Ho3+, Sc3+, Al3+, Y3+, Yb3+, Lu3+, Eu3+, may be mentioned.
The cation may also be an organometallic cation, such as a metallocenium. By way of example, the cations derived from ferrocene, titanocene, zirconocene, from an indenocenium or a metallocenium arene, cations of transition metals complexed with ligands of phosphine type possibly having a chirality, organometallic cations having one or more alkyl or aryl groups covalently fixed to an atom or a group of atoms, may be mentioned. Specific examples include methylzinc, phenylmercury, trialkyltin or trialkyllead, chloro[ethylene-bis(indenyl)] zirconium (IV) or tetrakis-(acetonitrile)palladium(II). The organo-metallic cation may be part of a polymer chain.
In a specific embodiment of the invention, the organic cation is an onium cation selected from the group consisting of R3O+(oxonium), NR4+(ammonium), RC(NHR2)2+(amidinium), C(NHR2)3+(guanidinium), C5R6N+(pyridinium), C3R5N2+(imidazolium), C3R7N2+(imidazolinium), C2R4N3+(triazolium), SR3+(sulfonium), PR4+(phosphonium), IR2+(iodonium), (C6R5)3C+(carbonium) cations. In a given onium cation, the radicals R may all be similar. However, an onium cation may also include radicals R which are different from one another. A radical R may be a H or it may be selected from the following radicals:
alkyl, alkenyl, oxa-alkyl, oxa-alkenyl, aza-alkyl, aza-alkenyl, thia-alkyl, thia-alkenyl, aryl, arylalkyl, alkylaryl, alkenylaryl radicals, dialkylamino radicals and dialkylazo radicals;
cyclic or heterocyclic radicals possibly comprising at least one lateral chain comprising heteroatoms such as nitrogen, oxygen, sulfur;
cyclic or heterocyclic radicals possibly comprising heteroatoms in the aromatic nucleus;
groups comprising a plurality of aromatic or heterocyclic nuclei, condensed or non-condensed, possibly containing at least one nitrogen, oxygen, sulfur or phosphorus atom.
When an onium cation carries at least two radicals R which are different from H, these radicals may together form a cycle which is aromatic or non-aromatic, possibly enclosing the center carrying the cationic charge.
When the cationic part of a compound of the invention is an onium cation, it may be either in the form of an independent cationic group which is bound to the cationic part only by the ionic bond between the positive charge of the cation and the negative charge of the anionic part. In this case, the cationic part may be part of a recurring unit of a polymer.
An onium cation may also be part of the radical Z or the radical RD carried by the anionic center. In this case, a compound of the invention constitutes a zwitterion. When the cation of a compound of the invention is an onium cation, it may be selected so as to introduce in the compound substituents enabling to give specific properties to said compound. For example, the cation M+ may be a cationic heterocycle with aromatic character, including at least one alkylated nitrogen atom in the cycle. By way of example, an imidazolium, a triazolium, a pyridinium, a 4-dimethyl-amino-pyridinium may be mentioned, said cations possibly carrying a substituent on the carbon atoms of the cycle. Among these cations, those in which the salts have a melting point lower than 150xc2x0 C., more particularly lower than 25xc2x0 C.
A compound of the invention in which the cation M is a group carrying a diazoic group having xe2x80x94Nxe2x95x90Nxe2x80x94, xe2x80x94Nxe2x95x90N+, a sulfonium group, an iodonium group, a phosphonium group or a substituted or non-substituted arene-ferrocenium cation, possibly incorporated in the polymeric network, is interesting inasmuch as it is activatable by a source of actinic energy of suitable wavelength. Specific examples of such compounds include those in which the cation is a diaryliodonium cation, a dialkylaryliodonium cation, a triarylsulfonium cation, a trialkylaryl sulfonium cation, or a substituted or non-substituted phenacyl-dialkyl sulfonium cation. The above cations may be part of a polymer chain.
The cation M of a compound of the invention may be an organic cation incorporating a group 2,2xe2x80x2[azobis(2-2xe2x80x2-imidazolinio-2-yl)propane]2+ or 2,2xe2x80x2-azobis(2-amidiniopropane)2+. The compound the invention is then particularly interesting as a free radical initiator, which is thermally activatable and non-volatile, soluble in polar organic solvents and in aprotic solvating monomers and polymers.
A specific family of compounds of the invention is the one which comprises a group RDYxe2x80x94. The compounds in which Y is xe2x80x94SO2xe2x80x94 or xe2x80x94COxe2x80x94 are especially preferred.
The choice of substituent RD enables to adjust the properties of a compound of the invention. In an embodiment, RD is selected from alkyl, alkenyl, oxa-alkyl, oxa-alkenyl, aza-alkyl, aza-alkenyl, thia-alkyl or thia-alkenyl having 1 to 24 carbon atoms, or from aryl, arylalkyl, alkylaryl or alkenylaryl radicals having 5 to 24 carbon atoms.
According to another embodiment, RD is selected from alkyl or alkenyl radicals having 1 to 12 carbon atoms and possibly comprising at least one heteroatom O, N or S in the main chain or in a lateral chain, and/or possibly carrying a hydroxy group, a carbonyl group, an amine group or a carboxyl group.
According to another embodiment, RD is selected from aryl, arylalkyl, alkylaryl or alkenylaryl radicals, in which the aromatic nuclei and/or their substituents comprise heteroatoms such as nitrogen, oxygen, sulfur.
Substituent RD may be a polymer radical, for example a poly(oxyalkylene) radical. A compound of the invention is then in the form of a polymer carrying an ionic group xe2x80x94Yxe2x80x94C(CN)2xe2x88x92, M+.
RD may be a recurring unit of a polymer, for example an oxyalkylene unit or a styrene unit. The compound of the invention is then in the form of a polymer in which at least part of the recurring units carry a lateral group on which an ionic group xe2x80x94Yxe2x80x94C(CN)2xe2x88x92, M+ is fixed. By way of example, there may be mentioned a poly(oxyalkylene) in which at least certain oxyalkylene units carry a substituent xe2x80x94Yxe2x80x94C(CN)2xe2x88x92, M+ or a polystyrene in which at least certain styrene units carry a substituent xe2x80x94Yxe2x80x94C(CN)2xe2x88x92, M+.
A particular category of compounds according to the invention comprises the compounds in which substituent RD has at least one anionic ionophorous group and/or at least one cationic ionophorous group. The anionic group may for example be a carboxylate function (xe2x80x94CO2xe2x88x92), a sulfonate function (xe2x80x94SO3xe2x88x92), a sulfonimide function (xe2x80x94SO2NSO2xe2x80x94) or a sulfonamide function (xe2x80x94SO2Nxe2x80x94). The ionophorous group may for example be an iodonium, sulfonium, oxonium, ammonium, amidinium, guanidinium, pyridinium, imidazolium, imidazolinium, triazolium, phosphonium or carbonium group. The cationic ionophorous group may act totally or partially as a cation M.
When RD includes at least one ethylenic unsaturation and/or a condensable group and/or a dissociable group by thermal means, by photochemical means or by ionic dissociation, the compounds of the invention are reactive compounds which may be subject to polymerizations, cross-linkings or condensations, possibly with other monomers. They may also be used to fix ionophorous groups on the polymers carrying a suitable reactive function.
A substituent RD may be a mesomorphous group or a chromophore group or a self-doped electronically conductive polymer or a hydrolyzable alkoxysilane.
A substituent RD may include a group capable of trapping free radicals, for example a hindered phenol or a quinone.
A substituent RD may also include a dissociating dipole, for example an amide function, a sulfonamide function or a nitrile function.
A substituent RD may also include a redox couple, a disulfide group, a thioamide group, a ferrocene group, a phenothiazine group, a bis(dialkylaminoaryl) group, a nitroxide group or an aromatic imine group.
A substituent RD may also include a complexing ligand, or an optically active group.
Another category of compounds of the invention comprises compounds in which Y is a carbonyl group, RDxe2x80x94COxe2x80x94 representing an amino acid, or an optically or biologically active polypeptide.
According to another variant, a compound according to the invention comprises a substituent RD which represents a radical having a valency v higher than 2, itself including at least one group xe2x80x94Yxe2x80x94C(CN)2xe2x88x92, M+. In this case, the negative charges which are present on the anionic part of the compound of the invention should be compensated by the appropriate number of cations or cationic ionophorous groups M.
When a compound of the present invention corresponds to the formula Zxe2x80x94C(CN)2xe2x88x92, M+ in which Z is an electroattractor group which is not bonded to the nitrogen atom carrying the negative charge by means of a group xe2x80x94SOxxe2x80x94, Z is advantageously selected from the group consisting of xe2x80x94OCnF2n+1, xe2x80x94OC2F4H, xe2x80x94SCnF2n+1 and xe2x80x94SC2F4H, xe2x80x94OCFxe2x95x90CF2, xe2x80x94SCFxe2x95x90CF2, n being a whole number from 1 to 8. Z may also be a radical CnF2n+1CH2xe2x80x94, n being a whole number from 1 to 8.
The compounds of the invention may be obtained by a process in which a compound RDxe2x80x94Yxe2x80x94L or Zxe2x80x94L is reacted with a compound [Axe2x80x94C(CN)2]nxe2x88x92mnMxe2x80x2m+,
Z and RD being such as defined previously,
Mxe2x80x2 being H or a cation such as defined previously for M,
L represents an electronegative starting group such as a halogen, a N-imidazoyl radical, a N-triazoyl radical, a compound giving an activated ester (for example a succinimidyloxy, a benzotriazoloxy or a O-acylurea), an alkoxide group, a RDxe2x80x94Yxe2x80x94Oxe2x80x94 group or a RDxe2x80x94Yxe2x80x94Sxe2x80x94 group, and
A represents a cation Mm+, a trialkylsilyl group, a trialkyl germanyl group, a trialkylstannyl group or a tertioalkyl group, in which the alkyl substituents have 1 to 6 carbon atoms.
By way of example, there should be mentioned the reaction of a flurosulfonyl fluoride with a di-salt of malononitrile according to the following reaction scheme:
FSO2xe2x80x94F+[NaC(CN)2]xe2x88x92Na+xe2x86x92NaF+[FSO2xe2x80x94C(CN)2]xe2x88x92Na+.
The use of a compound [Axe2x80x94C(CN)2]nxe2x88x92mnMxe2x80x2m+ in which A is a tertioalkyl group is advantageous, since such a group is a proton precursor by formation of the corresponding alkene. The use of the trialkylsilyl group is especially interesting when the starting group is a fluorine, due to the very high stability of the bond Fxe2x80x94Si.
When a compound [Axe2x80x94C(CN)2]nxe2x88x92mnMxe2x80x2m+ in which A is the proton is used, it is advantageous to carry out the reaction in the presence of a tertiary base or a congested base T capable of forming the salt Lxe2x88x92(HT+) by combination with the proton, in order to promote the formation of the compound of the invention. The base may be selected among alkylamides (for example triethylamine, di-isopropylamine, quinuclidine), 1,4-diazobicyclo[2,2,2]octane (DABCO); pyridines (for example pyridine, alkylpyridines, dialkylaminopyridines); imidazoles (for example N-alkylimidazoles, imidazo[1,1-a]pyridine); amidines (for example 1,5-diazabicyclo[4,3,0]non-5-ene (DBN), 1,8-diazabicyclo[5,4,0]undec-7-ene (DBU)); guanidines (for example tetramethyl guanidine, 1,3,4,7,8-hexahydro-1-methyl-2H-pyrimido[1,2-a]pyrimidine (HPP). An alkali metal salt of malononitrile can also be used as a base.
By way of example of such a process, the process in which a carbonyl chloride RDCOCl is reacted with malononitrile in the presence of DABCO may be mentioned.
A compound of the invention may also be obtained by direct coupling between a malononitrile salt and a carboxylic acid by means of a coupling agent. When Z=CO, it is advantageous to use a compound RZX of the type pseudo-halide directly prepared in-situ (X=RCO2, SCO, PTO, BzO . . . ) from RCOOH by action of the condensation agents used in the synthesis of peptides (molecular dehydrating agents). Such agents are described for example in Synthesis p. 453 (1972) and in Ann. Rev. Biochem 39, 841 (1970). The compounds of the invention are then prepared from RCOOH to which the molecular dehydration agent is added, and also the compound (1/nM)[(NC)2CH] in stoichiometric proportions in a polar solvent. Preferably, the condensation agent is selected from carbodiimides, for example cyclohexyl carbodiimide or diisopropyl carbodiimide; carbonates and oxalates of succinimidyl, phthalimidyl, benzotriazolyl, of nitro-, dinitro- or perhalo-phenols, of trifluoroethyl, of trichloroethyl; the mixture Pxcfx863-diethylazodicarboxylate (DEAD) or Pxcfx863-dithiodipyridine; carbonyldiimidazole (Im)2CO or phenylphosphorodiimidazole xcfx86PO(Im)2; amide acetals, for example dimethylformamide di-neopentyl acetal (CH3)2NCH[OCH2C(CH2)2]2; 2-alcoxy-1-alkoxycarbonyl-1,2-dihydroquinoline; salts of O-benzo triazol-1-yl-N,N,Nxe2x80x2,Nxe2x80x2-tetramethyluronium or O-benzo triazol-1-yloxytrisdimethylaminophosphonium; aromatic sultones, for example 2,2-(6-nitronaphth[1,8-cd]-1,2-oxathiazoyl) oxide, iosbutyl chloroformate, diphenylphosphochloroiridate, ethylene chlorophosphite, diethylethylene pyrophosphite, bis(2-oxo-3-oxazolidinyl)phosphinyl chloride; 2-ter-butyl-5-methyl isooxazolium salts (Woodward""s reagent L).
The cation of the compound obtained according to either of the processes described above may be replaced by the known processes of cationic exchange, either by precipitation or selective extractions, or by the use of ion exchange resins.
In addition, the substituent RD of a compound of the invention may be modified by known reactions. For example, a substituent RD which comprises an allyl group maybe converted by reaction with a peroxide to give an expoxidized substituent RD. A group xe2x80x94NHR may be converted into a vinylester group by reaction with potassium tert-butoxide and vinylchloroformate. Processes to carry out these modifications and others are available to one skilled in the art.
The ionic compounds of the present invention comprise at least one ionophorous group on which substituents of highly various natures are fixed. Bearing in mind the large possible choice for the substituents, the compounds of the invention enable to provide properties of ionic conduction in most organic, liquid or polymer medias having even a low polarity. The applications are important in the field of electrochemistry, in particular for storing energy in primary or secondary generators, in supercapacitances, in combustible batteries and in electroluminescent diodes. The compatibility of the ionic compounds of the invention with polymers or organic liquids enables to provide noted antistatic properties, even when the amount of ionic compound is extremely low. The compounds of the invention which are polymers, as well as polymeric compounds obtained from the compounds of the invention having the property of polymerizing or copolymerizing, have the properties listed above with the advantage of having an unmovable anionic charge. This is why another object of the present invention consists of an ionically conductive material made of an ionic compound of the present invention in solution in a solvent.
According to an embodiment, the ionic compound used for preparing an ionically conductive material is selected from compounds in which the cation is ammonium, or a cation derived from a metal, in particular lithium or potassium, zinc, calcium, rare earth metals, or an organic cation, such as a substituted ammonium, an imidazolium, a triazolium, a pyridinium, a 4-dimethylamino-pyridinium, said cations possibly carrying a substituent on the carbon atoms of the cycle. The ionically conductive material thus obtained has a high conductivity and solubility in solvents, due to the low interactions between the positive charge and the negative charge. Its range of electrochemical stability is wide, and it is stable in reducing as well as oxidizing media. Moreover, the compounds which have an organic cation and a melting point lower than 150xc2x0 C., in particular compounds of imidazolium, triazolium, pyridinium, 4-dimethylamino-pyridinium have a high intrinsic conductivity, even in the absence of solvents when they are in molten phase.
The properties of the ionically conductive material may also be modified by the choice of substituent Y or RD.
The choice of an alkyl group, an aryl group, an alkylaryl group or an arylalkyl group for RD enable to provide in the ionically conductive material properties of the type mesogene, in particular alkyl groups containing 6 to 20 carbon atoms, arylalkyl groups, in particular both containing the biphenyl entity which form phases of the liquid crystal type. Properties of conduction in phases of the liquid crystal, nematic, cholesteric or discotic type are interesting for applications concerning optical postings or for reducing the mobility of anions in electrolytes, in particular in polymer electrolytes, without affecting the mobility of the cations. This characteristic is important for applications in electrochemical generators, in particular those utilizing lithium cations.
When the substituent RD contains mesomorphous group or a group to comprising at least one ethylenic unsaturation and/or a condensable group and/or a group which is dissociable by thermal means, by photochemical means or by ionic dissociation, the ionically conductive material easily forms polymers or copolymers which are polyelectrolytes, the latter being intrinsically polyelectrolytes when the polymer carries solvating groups, or becomes polyelectrolytes by addition of a is polar solvent of the liquid or polymer type, or by mixture with such a solvent. These products have a conductivity which is solely due to the cations, which constitutes a property which is very useful in applications of the electrochemical generator type. In low molar fraction in a copolymer, they give rise to stable antistatic properties which are hardly dependent on humidity and cause the fixation of cationic colorants, this property being useful for textile fibers and lasers with coloring materials.
The presence of a substituent RD which is a self-doped electronically conductive polymer improves the stability of the ionically conductive material with respect to outside agents. The conductivity is stable in time even at high temperatures. In contact with metals, these materials give very low interface resistances and protect in particular ferrous metal or aluminum from corrosion.
When the substituent RD is a hydrolyzable alkoxysilane, the ionically conductive material may form stable polymers by a simple mechanism of hydrolysis-condensation in the presence of water, thus enabling to treat surfaces of oxides, of silica, of silicates, in particular glass, to induce properties of surface conduction, antistatic properties, or to promote the adhesion of polar polymers.
When the substituent RD is a group comprising a free radical trap such as a hindered phenol, or a quinone, the ionically conductive material has the following advantages and properties: it acts as an antioxidant having no volatility and being compatible with polar monomers and polymers, to which it also gives antistatic properties.
When the substituent RD comprises a dissociating dipole such as an amide, a sulfonamide or a nitrile, the ionically conductive material has an improved conductivity in media of low or medium polarity, in particular in solvating polymers, which enables to minimize, even to prevent the addition of solvents or of volatile plasticizing agents.
The presence of a substituent RD which contains a redox couple such as a disulfide, a thioamide, a ferrocene, a pheno-thiazine, a bis(dialkylaminoaryl) group, a nitroxide, an aromatic imide, enables to induce in the ionically conductive material properties of redox shuttle useful as protective elements and charge equalization of electrochemical generators, in photoelectrochemical systems, in particular in systems of conversion of light into electricity, in systems of modulation of light of the electrochrome type.
The presence of a substituent RD which is a complexing ligand in an ionically conductive material enables to chelate metallic cations, in particular those which have an elevated charge (2, 3 and 4), in the form of soluble complex in organic media, including in aprotic media, and enables the transport of these cations in particular in the form of anionic complex, in solvating polymers. The metallic cations of elevated charge are indeed immovable in solvating polymers. This type of complexing agents gives with certain cations of transition metals (Fe, Co . . . ) or certain rare earths (Ce, Eu . . . ) redox couples which are particularly stable. ionically conductive materials containing a compound of the invention in which RD is an alkyl or alkenyl substituent which contains at least one heteroatom selected from O, N and S have a complexing and plasticizing capacity, in particular in polar polymers and especially polyethers. The heteroatoms N and S are selectively complexing for cations of transition metals Zn and Pb.
When an alkyl or alkenyl substituent RD additionally carries a hydroxy group, a carbonyl group, an amine group, a carboxyl group, the ionic compound of the invention may give by polycondensation a polymer or a copolymer and the ionically conductive material which contains such a polymer or copolymer have polyelectrolytic properties.
The presence, in a ionically conductive material of the invention, of a compound in which RD is selected from aryl, arylalkyl, alkylaryl or alkenylaryl radicals, in which the lateral chains and/or the aromatic nuclei comprise heteroatoms such as nitrogen, oxygen, sulfur, improves dissociation and increases the possibility of producing complexes depending on the position of the heteroatom (pyridine) or of giving by duplicative oxidation conjugated polymers or copolymers (pyrrol, thiophene).
When the ionically conductive material contains a compound of the invention in which RD represents a recurring unit of a polymer chain, the material constitutes a polyelectrolyte.
A compound of the invention in which the substituent Z is selected from the group consisting of xe2x80x94OCnF2n+1, xe2x80x94OC2F4H, xe2x80x94SCnF2n+1 and xe2x80x94SC2F4H, xe2x80x94OCFxe2x95x90CF2, xe2x80x94SCFxe2x95x90CF2, n being a whole number from 1 to 8, is a precursor of stable monomers and polymers, in particular towards oxygen even at elevated temperatures of 80xc2x0 C. when dealing with polymers. An ionically conductive material which contains such a compound is therefore particularly appropriate as an electrolyte of a combustible battery.
An ionically conductive material of the present invention comprises an ionic compound of the invention in solution in a solvent.
The solvent may be an aprotic liquid solvent, a polar polymer or one of their mixtures.
The aprotic liquid solvent is selected for example from linear ethers and cyclic ethers, esters, nitriles, nitro derivatives, amides, sulfones, sulfolanes, alkylsulfamides and partially hydrogenated hydrocarbons. The solvents which are particularly preferred are diethylether, dimethoxyethane, glyme, tetrahydrofurane, dioxane, dimethyltetrahydrofurane, methyl or ethyl formate, propylene or ethylene carbonate, alkyl carbonates (such as dimethylcarbonate, diethylcarbonate and methylpropylcarbonate), butyrolactones, acetonitrile, benzonitrile, nitromethane, nitrobenzene, dimethylformamide, diethylformamide, N-methylpyrrolidone, dimethylsulfone, tetramethylene sulfone, tetramethylene sulfone and tetraalkylsulfonamides having 5 to 10 carbon atoms.
An ionically conductive material of the present invention may simultaneously comprise an aprotic liquid solvent selected from the aprotic liquid solvents mentioned above and a polar polymer solvent comprising units containing at least one heteroatom selected from sulfur, nitrogen, oxygen and fluorine. It may comprise from 2 to 98% liquid solvent. By way of example of such a polar polymer, polymers which mainly contain units derived from acrylonitrile, vinylidene fluoride, N-vinylpyrrolidone or methylmethacrylate may be mentioned. The proportion of aprotic liquid in the solvent may vary from 2% (corresponding to a plasticized solvent) to 98% (corresponding to a gelled solvent).
An ionically conductive material of the present invention may additionally contain a salt commonly used in the prior art to prepare an ionically conductive material. Among the salts which may be used in admixture with an ionic compound of the invention, a salt selected from perfluoroalcanesulfonates, bis(perfluoroalkylsulfonyl) imides, bis(perfluoroalkylsulfonyl) methanes and tris(perfluoroalkylsulfonyl) methanes are particularly preferred.
Of course, an ionically conductive material of the invention may additionally contain additives normally used in this type of material, such as mineral or organic charges in the form of a powder or fibers.
An ionically conductive material of the invention may be used as electrolyte in an electrochemical general. The present invention thus has as an object an electrochemical generator comprising a negative electrode and a positive electrode separated by an electrolyte, characterized in that the electrolyte is an ionically conductive material as defined above. According to a particular embodiment, such a generator comprises a negative electrode consisting of metallic lithium, or an alloy thereof, possibly in the form of a nanometric dispersion in lithium oxide, or a double nitride of lithium and a transition metal, or a low potential oxide having the general formula Li1+y+x/3Ti2xe2x88x92x/3O4 (0xe2x89xa6xxe2x89xa61, 0xe2x89xa6yxe2x89xa61), or carbon and the carbonated products resulting from the pyrolysis of organic materials. According to another embodiment, the generator comprises a positive electrode selected from vanadium oxides VOx (2xe2x89xa6xxe2x89xa62,5), LiV3O8, LiyNi1xe2x88x92xCoxO2, (0xe2x89xa6xxe2x89xa61; 0xe2x89xa6yxe2x89xa61), manganese spinels LiyMn1xe2x88x92xMxO2 (M=Cr, Al, V, Ni, 0xe2x89xa6xxe2x89xa60,5; 0xe2x89xa6yxe2x89xa62), organic polydisulfides, FeS, FeS2, iron sulfate Fe2(SO4)3, iron and lithium phosphates and phosphosilicates of olivine structure, or substituted products wherein iron is substituted by manganese, used alone or in admixtures. The collector of the positive is preferably made of aluminum.
An ionically conductive material of the present invention may also be used in a supercapacitance. Another object of the present invention is consequently to provide a supercapacitance utilizing at least one carbon electrode of high specific surface, or an electrode containing a redox polymer, in which the electrolyte is an ionically conductive material as defined above.
An ionically conductive material of the present invention may also be used for the p or n doping of an electronically conductive material and this use constitutes another object of the present invention.
In addition, an ionically conductive material of the present invention may be used as an electrolyte in an electrochrome device. An electrochrome device in which the electrolyte is an ionically conductive material according to the invention is another object of the present invention.
It was observed that the strong dissociation of ionic species of compounds of the invention results in a stabilization of carbocations, in particular those in which there is a conjugation with oxygen and nitrogen and, surprisingly, in a strong activity of the proton form of the compounds of the invention on certain monomers. The present invention therefore also has as an object the use of the ionic compounds as photoinitiators which constitute sources of Brxc3x8nsted acids, which are catalysts for the polymerization or cross-linking of monomers or polymers capable of cationic reaction, or as catalysts for the modification of polymers.
The process of polymerization or cross-linking of monomers or prepolymers capable of cationic reaction is characterized in that there is used a compound of the invention as photoinitiator constituting a source of acid catalyzing the polymerization reaction. The compounds according to the invention in which the cation is a group having a bond xe2x80x94Nxe2x95x90N+, xe2x80x94Nxe2x95x90Nxe2x80x94, a sulfonium group, an iodonium group, or an arene-ferrocenium cation which is substituted or non-substituted, possibly incorporated in a polymeric network, are particularly preferred.
The choice of substituent RD or substituent Z is made so as to increase the solubility of said compound in the solvents used for the reaction of monomers or prepolymers, and as a function of the desired properties for the final polymer. For example, the choice of non-substituted alkyl radicals gives a solubility in low polar media. The choice of radicals comprising an oxa group or a sulfone will give a solubility in polar media. The radicals including a sulfoxide group, a sulfone group, a phosphine oxide group, a phosphonate group, respectively obtained by the addition of oxygen on the atoms of sulfur or phosphorus, may give to the polymer obtained improved properties with respect to adhesion, shine, resistance to oxidation or to UV. The monomers and prepolymers which may be polymerized or cross-linked with the photoinitiators of the present invention are those which may undergo a cationic polymerization.
The monomers and prepolymers which may be polymerized or cross-linked with the photoinitiators of the present invention are those which may be subject to cationic polymerization.
Among the monomers, monomers which include a cyclic ether function, a cyclic thioether function or cyclic amine function vinyl compounds (more particularly vinyl ethers), oxazolines, lactones and lactames may be mentioned.
Among the polymers of the ether or cyclic thioether type, ethylene oxide, propylene oxide, oxetane, epichlorhydrin, tetrahydrofurane, styrene oxide, cyclohexene oxide, vinylcyclohexene oxide, glycidol, butylene oxide, octylene oxide, glycidyl ethers and esters (for example glycidyl methacrylate or acrylate, phenyl glycidyl ether, diglycidylether of bisphenol A or its fluorinated derivatives), cyclic acetals having 4 to 15 carbon atoms (for example dioxolane, 1,3-dioxane, 1,3-dioxepane) and spiro-bicyclo dioxolanes may be mentioned.
Among vinyl compounds, vinyl ethers constitute a very important family of monomers which are capable of cationic polymerization. By way of example, there may be mentioned ethyl vinyl ether, propyl vinyl ether, isobutyl vinyl ether, octadecyl vinyl ether, ethyleneglycol monovinyl ether, diethyleneglycol divinyl ether, butanediol monovinyl ether, butanediol divinyl ether, hexanediol divinyl ether, ethyleneglycol butyl vinyl ether, triethyleneglycol methyl vinyl ether, cyclohexanedimethanol monovinyl ether, cyclohexanedimethanol divinyl ether, 2-ethylhexyl vinyl ether, poly-THF-divinyl ether having a molecular weight between 150 and 5,000, diethyleneglycol monovinyl ether, trimethylolpropane trivinyl ether, aminopropyl vinyl ether, 2-diethylaminoethyl vinyl ether.
Other vinyl compounds may include, by way of example, 1,1-dialkylethylenes (for example isobutene), vinyl aromatic monomers (for example styrene, xcex1-alkylstyrenes, such as xcex1-methylstyrene, 4-vinylanisole, acenaphthene) N-vinyl compounds (for examples N-vinylpyrolidone or N-vinyl sulfonamides).
Among prepolymers, there may be mentioned compounds in which epoxy groups are carried by an aliphatic chain, an aromatic chain, or a heterocyclic chain, for example glycidicethers of bisphenol A which are ethoxylated by 3 to 15 ethylene oxide units, siloxanes having lateral groups of the epoxycyclohexene-ethyl type obtained by hydrosilylation of copolymers of dialkyl, alkylaryl or diaryl siloxane with methyl hydrogenosiloxane in the presence of vinylcyclohexene oxide, condensation products of the sol-gel type obtained from triethoxy or trimethoxy silapropylcyclohexene oxide, urethanes incorporating the reaction products of butanediol monovinylether and an alcohol of a functionality higher than or equal to 2 with an aliphatic or aromatic di- or tri-isocyanate.
The process of polymerization according to the invention consists in mixing at least one monomer or prepolymer capable of cationic polymerization and at least one ionic compound of the invention, and subjecting the mixture obtained to actinic or xcex2 radiation. Preferably, the reaction mixture is subjected to radiation having been formed into a thin layer having a thickness lower than 5 mm, preferably in the form of a thin layer having a thickness lower than or equal to 500 xcexcm. The duration of the reaction depends on the thickness of the sample and the power of the source at the active xcex wavelength. It is defined by the speed at which it passes in front of the source, which is between 300 mm/min and 1 cm/min. Layers of the final material having a thickness greater than 5 mm may be obtained by repeating many times the operation consisting in spreading a layer and treating it with the radiation.
Generally, the quantity of photoinitiator used is between 0.01 and 15% by weight with respect to the weight of the monomer or prepolymer, preferably between 0.1 and 5% by weight.
An ionic compounds of the present invention may be used as photoinitiator in the absence of solvent, for example when it is intended to polymerize liquid monomers in which the ionic compound used as photoinitiator is soluble or easily dispersible. This type of utilization is particularly interesting, since it enables to overcome the problems associated with solvents (toxicity, flammability).
An ionic compound of the present invention may also be used as photoinitiator in the form of a homogeneous solution in a solvent which is inert towards polymerization, ready to be used and easily dispersible, in particular in the case where the medium to be polymerized or cross-linked has a high viscosity.
As example of an inert solvent, there may be mentioned volatile solvents, such as acetone, methyl-ethyl ketone and acetonitrile. These solvents will be used simply to dilute the products to be polymerized or cross-linked (to make them less viscous, especially when dealing with a prepolymer). They will be removed by drying after polymerization or cross-linking. Non-volatile solvents may also be mentioned. A non-volatile solvent also serves to dilute the products that one wishes to polymerize or cross-link, and to dissolve the ionic compound of the invention used as photoinitiator, however, it will remain in the material formed and will thus act as plasticizing agent. By way of example, propylene carbonate, xcex3-butyrolactone, ether-esters of mono-, di-, tri-ethylene or propylene glycols, ether-alcohols of mono-, di-, tri-ethylene or propylene glycols, plasticizing agents such as esters of phthalic acid or citric acid, may be mentioned.
According to another embodiment of the invention, there may be used as solvent or diluent a compound which is reactive towards polymerization, which is a compound of low molecular weight and of low viscosity which will simultaneously act as polymerization monomer and solvent or diluent for more viscous polymers or prepolymers used in combination. After the reaction, these monomers having been used as solvent will be part of the macromolecular network finally obtained, their integration being wider when dealing with bi-functional monomers. The material obtained after irradiation is now free of products having a low molecular weight and a substantial vapour tension, or capable of contaminating objects with which the polymer is in contact. By way of example, a reactive solvent may be selected from mono and divinyl ethers of mono-, di-, tri-, tetra-ethylene and propylene glycols, N-methylpyrolidone, 2-propenylether of propylene carbonate commercially available for example under the commercial designation PEPC from ISP, New Jersey, United States.
To irradiate the reaction mixture, the irradiation may be selected from ultraviolet radiation, visible radiation, X-rays, xcex3 rays and xcex2 radiation. When ultraviolet light is used as actinic radiation, it may be advantageous to add to the photoinitiators of the invention photosensitizers intended to provide an efficient photolysis with wavelengths less energetic than those corresponding to the maximum of absorption of the photoinitiator, such as those produced by industrial devices, (I≈300 nm for mercury vapour lamps in particular). Such additives are known, and by way of non-limiting example, there may be mentioned anthracene, diphenyl-9,10-anthracene, perylene, phenothiazine, tetracene, xanthone, thioxanthone, acetophenone, benzophenone, 1,3,5-triaryl-2-pyrazolines and derivatives thereof, in particular derivatives which are substituted on the aromatic nuclei by alkyl, oxa- or aza-alkyl radicals, enabling inter alia to change the absorption wavelength. Isopropylthioxantone is an example of preferred photosensitizer when an iodonium salt according to the invention is used as photoinitiator.
Among the different types of radiation mentioned, ultraviolet radiation is particularly preferred. On the one hand, it is more convenient to use than the other radiations mentioned. On the other hand, photoinitiators are in general directly sensitive towards UV rays and photosensitizers are more efficient when the difference of energy (xcex4xcex) is lower.
The ionic compounds of the invention may also be used in association with free radical initiators produced thermally or by action of actinic radiation. It is also possible to polymerize or cross-link mixtures of monomers or polymers containing functions in which the types of polymerization are different, for example, monomers or prepolymers which polymerize by free radical and monomers or prepolymers which polymerize by cationic polymerization. This possibility is particularly advantageous to produce interpenetrated networks having physical properties which are different from those which would be obtained by a simple mixture of polymers originating from corresponding monomers. Vinyl ethers are not or are very little active by free radical initiation. It is therefore possible, in a reaction mixture containing a photoinitiator according to the invention, a free radical initiator, at least one monomer of the vinyl ether type and at least one monomer comprising non-activated double bonds such as those of the allyl groups, to carry out a separate polymerization of each type of monomer. On the other hand, it is known that monomers which are lacking in electrons, such as esters or amides of furmaric acid, maleic acid, acrylic or methacrylic acid, itaconic acid, acrylonitrile, methacrylonitrile, maleimide and derivatives thereof, form in the presence of vinyl ethers which are enriched in electrons, complexes of transfer of charge giving alternated polymers 1:1 by free radical initiation. An initial excess of vinyl monomers with respect to this stoichiometry enables to preserve polymerizable functions by pure cationic initiation. The start of the activity of a mixture of free radical initiator and cationic initiator according to the invention may be carried simultaneously for the two reactants in the case for example of isolation by actinic radiation of a wavelength for which the photoinitiators of the invention and the selected radical initiators are active, for example at xcex=250 nm. By way of example, the following commercial products: Irgacure 184(copyright), Irgacure 651(copyright), Irgacure 261(copyright), Quantacure DMB(copyright), Quantacure ITX(copyright) may be mentioned as initiators.
It may also be advantageous to use the two types of polymerization in a sequential manner, to first form prepolymers which are easy to shape and in which hardening, adhesion, solubility as well as degree of cross-linking may be modified by initiating the activity of the cationic initiator. For example, a mixture of a thermo-dissociable radical initiator and a cationic photoinitiator according to the invention enables to provide sequential polymerizations or cross-linking, first under the action of heat, then under the action of actinic radiation. Similarly, if a free radical initiator and a cationic photoinitiator according to the invention are selected, the first being photosensitive at longer wavelengths than the one initiating the photoinitiator according to the invention, there is obtained a cross-linking in two controllable steps. Free radical initiators may for example be Irgacure(copyright) 651 enabling to initiate free radical polymerizations at wavelength of 365 nm.
The invention also has as an object the use of ionic compounds of the invention for chemical amplification reactions of photoresists in the field of microlithography. During such use, a film of a material comprising a polymer and an ionic compound of the invention is subject to irradiation. The irradiation causes the formation of the acid by replacement of the cation M with a proton, which catalyzes the decomposition or transformation of the polymer. After decomposition or transformation of the polymer on the parts of the film which have been irradiated, the monomers formed or the polymer which has been converted are removed and what remains is an image of the unexposed parts. For this particular application, it is advantageous to use a compound of the invention which is in the form of a polymer consisting essentially of styrenyl recurring units carrying an ionic substituent xe2x80x94C(CN)2xe2x88x92. These compounds enable to obtain after photolysis products which are not volatile, and therefore not odoriferous when dealing with sulfides. Among the polymers which may thus be modified in the presence of a compound of the invention, there may for example be cited polymers containing ester units or tertiaryalkyl arylether units, for example poly(phthaldehydes), polymers of bisphenol A and a diacid, polytertiobutoxycarbonyl oxystyrene, polytertiobutoxy-xcex1-methyl styrene, polyditertiobutylfumarate-co-allyltrimethylsilane and polyacrylates of a tertiary alcohol, in particular tertiobutyl polyacrylate. Other polymers are described in J. V. Crivello et al, Chemistry of Materials 8, 376-381, (1996).
The ionic compounds of the present invention, which have an elevated thermal stability, give numerous advantages with respect to the known salts of the prior art. They have speeds of initiation and propagation which are comparable or higher than those obtained with coordination anions of the type PF6xe2x80x94, AsF6xe2x80x94 and especially SbF6xe2x80x94. In addition, the coefficient of diffusion of the anion xe2x80x94C(CN)2xe2x88x92 is higher than that of hexafluorometallate anions or tetrafluoroborate anions or phenylborate anions. These properties are explained by the delocalization of the negative charge and the weak repulsion between the partial charges carried by the nitrogen atoms of nitrile groups and removed from one another by 2xc3x85.
In the compounds of the present invention, the pairs of ions have a very high dissociation, which enables the expression of intrinsic catalytic properties of the cation Mm+, in which the active orbits are easily exposed to substrates of the reaction, especially in different media. Most of the important reactions of organic chemistry may thus be carried out under easy conditions, with excellent yields and the possibility of separating the catalyst from the reaction mixture. The demonstration of asymmetric induction by the use of an ionic compound according to the invention which carries a chiral group is particularly important in view of its generality and its ease of operation. The present invention consequently has as another object the use of compounds of the invention as catalysts in Friedel-Crafts reactions, Diels-Alder reactions, aldolization reactions, additions of Michael, reactions of allylation, reactions of pinacolic coupling, reaction of glycosilation, reaction of openings of the cycle of oxetanes, reactions of metathesis of alkenes, polymerizations of the Ziegler-Natta type, polymerizations of the metathesis type by cycle opening and polymerizations of the metathesis type of acyclic dienes. The preferred ionic compounds of the invention for utilization as catalyst for the above reactions are those in which the cation is selected from lithium, magnesium, copper, zinc, tin, trivalent metals, including rare earths, platinoids, and their organometallic couples, in particular metallocenes.
The compounds of the invention may also be used as solvent to carry out chemical, photochemical, electrochemical, photoelectrochemical reactions. For this particular use, the ionic compounds in which the cation is an imidazolium, triazolium, pyridinium or 4-dimethylamino-pyridinium, are preferred, said cation possibly carrying a substituent on the carbon atoms of the cycle. Among the compounds used in liquid form, those having a melting point lower than 150xc2x0 C., more particularly lower than 100xc2x0 C., are particularly preferred.
The inventors have also found that the ionic charge carried by the group xe2x80x94C(CN)2xe2x88x92 have a stabilizing effect on the electronic conductors of the conjugated polymer type, and that the use of the compound in which the substituent Z comprises a long alkyl chain enables to make these polymers soluble in known organic solvents even in doped state. Grafting of these charges on the polymer itself gives polymers with global cationic charge, which are soluble and present, in addition to their stability, anti-corrosion properties towards metal, such as aluminum and ferrous metals. It is an object of the present invention to provide materials with electronic conduction comprising an ionic compound of the present invention in which the cationic part is a polycation consisting of a doped xe2x80x9cpxe2x80x9d conjugated polymer. The preferred ionic compounds for this application are those in which the substituent Z or RD contains an alkyl chain having 6 to 20 carbon atoms.
The coloring materials of cationic type (cyanines) are used more and more frequently as sensitizers of photographic films, for storing optical information (optical disks accessible in writing), for lasers. The tendency of these conjugated molecules to pile over one another when they are in solid phase limits their utilization, because of the variation of the optical properties with respect to the isolated molecule. The use of ionic compounds of the invention for manufacturing cationic coloring materials including counter ions, possibly bound to this same molecule, correspond to functions of the invention enables to reduce phenomenons of aggregation, including in solid polymer matrices and to stabilize these coloring materials. It is another object of the present invention to provide a composition of cationic coloring material, characterized in that it contains an ionic compound according to the invention. The particularly preferred ionic compounds for this application are those in which the negative charge(s) of the anionic group xe2x80x94C(CN)2xe2x88x92 are either fixed to the molecule of the coloring material, or they constitute the counter-ion of the positive charges of the coloring material.
A few examples of compounds according to the invention are given hereinafter: 
The present invention is explained more in detail with the following examples, which describe the preparation and various utilizations of compounds of the invention. The invention is, however, not limited to these examples.
All the compounds of the invention have been prepared from alkali metal salts of malononitrile. Said salts have been obtained from commercial malononitrile previously purified in a sublimation cell at 40xc2x0 C. under secondary vacuum, the malononitrile being recovered after 48 hours on the cold finger of the cell, in the form of white crystals which are thereafter kept under argon.
The lithium salt was obtained by dosing an aqueous solution of malononitrile with a titrated solution of lithium hydroxide LiOH, the neutralization point being determined by means of a pH-meter. The aqueous solution was thereafter lyophilized, and the product was dried under secondary vacuum at room temperature during 72 hours. There is obtained a lithium salt which, kept under argon, has a purity determined by a proton and carbon RMN higher than 99%.
By the same process, sodium and potassium salts were obtained by replacing lithium hydroxide respectively with sodium hydroxide and potassium hydroxide.